Ruggedized optical fiber collimator

ABSTRACT

The present invention relates to a ruggedized optical fiber collimator. An embodiment of the present invention includes a housing, an optical fiber, a collimating lens system comprising at least one lens, and an inner tube. The optical fiber extends into the housing through the inner tube. The housing houses the inner tube and the collimating lens system. The optical fiber terminates in the housing. The housing, the optical fiber, the collimating lens system and the inner tube are arranged to perform the function of an optical fiber collimator. The inner tube is made from an optical fiber compatible material. Examples of the optical fiber compatible material include ruby, quartz, and sapphire.

FIELD OF THE INVENTION

[0001] This invention generally relates to optical fiber technology.Particularly, this invention relates to an improved ruggedized opticalfiber collimator for an optical fiber.

BACKGROUND OF THE INVENTION

[0002] Optical fiber technology is widely applied in communication,including telecommunication, data communication, cable television, andfiber-to-home applications. Optical fiber systems for some applications,including telecommunications and data communications, require highreliability and tolerance to harsh environments. The optical fibercollimator is a key component in an optical fiber system. It opticallycouples an optical fiber to an optical component. Optical fiber systems,in particular, optical fiber communication systems, employ a largequantity of optical fiber collimators because most optical fibersemployed in these systems are terminated with optical fiber collimators.To improve reliability and tolerance to harsh environments, highreliability optical fiber systems employ ruggedized components,including ruggedized optical fiber collimators.

[0003] There are numerous prior art optical fiber collimator designs. Inthe past, the most important design goal for passive optical componentswas optimal optical transmission performance because the laser signalsources employed in an optical fiber communication system were expensiveand not as reliable when compared to the passive components in thesystem, including optical fiber collimators. By optimizing thetransmission performance of passive optical components in an opticalcommunication system, the lowest power and therefore the least expensiveand more reliable laser signal source can be employed in the system.FIGS. 1 and 2 illustrate representative prior art optical fibercollimator designs. Many of these prior art designs are optimized foroptical transmission performance.

[0004]FIG. 1 shows a prior art optical fiber collimator design. Opticalfiber 107 attaches to fiber ferrule 1. Fiber ferrule 1 and collimatinglens 109 attach to housing 101. Housing 101 provides mechanical supportto fiber ferrule 1 and collimating lens 109. In the fabrication processof this optical fiber collimator, optical fiber 107 is inserted intofiber ferrule 1 and secured to fiber ferrule 1. The end of optical fiber107 and the end of fiber ferrule 1 are then polished to form opticalfiber termination 108. To reduce reflection and improve opticaltransmission performance, the surface of optical fiber termination 108is typically polished at an angle to the surface that is perpendicularto the axis of the fiber ferrule. The axis of the fiber ferrule isessentially the same as the optical axis of optical fiber 107 at opticalfiber termination 108. Collimating lens 109 is placed at a distance fromfiber termination 108. Similar to the surface at optical fibertermination 108, the surface of collimating lens 109 that is facingoptical fiber termination 108 is polished at an angle to the surfacethat is perpendicular to the optical axis of collimating lens 109. Thisangle is introduced to the lens design to reduce reflection and to matchthe corresponding angle of optical fiber 107 at optical fibertermination 108. Fiber ferrule 1 and collimating lens 109 are theninstalled into housing 101. Although it is not necessary, either fiberferrule or collimating lens 109 is secured to housing 101 to facilitatethe alignment process. After that, the distance between optical fibertermination 108 and collimating lens 109 is adjusted, and eithercollimating lens 109 or fiber ferrule 1 is rotated about its opticalaxis for optimal optical transmission performance. After the alignmentprocess, both fiber ferrule 1 and collimating lens 109 are secured tohousing 101. Conventional fiber ferrule 1 is typically made from acapillary tube. One skilled in the art readily understands that thereare numerous types of collimating lens or collimating lens systemdesigns, optical fiber termination and termination methods, housingdesigns, and fiber ferrule designs commonly employed in optical fibercollimators.

[0005]FIG. 2 shows another prior art design. It is a variation of thedesign shown in FIG. 1. Compared to the design shown in FIG. 1, thedesign shown in FIG. 2 has a multi-piece housing that includes firsthousing 3 and second housing 4. Referring to FIG. 2, optical fiber 107attaches to fiber ferrule 1 and collimating lens 109 attaches to secondhousing 4. Fiber ferrule 1 and second housing 4 attaches to firsthousing 3. Second housing 4 allows for the adjustment of the relativeoffset between the optical axes of optical fiber 107 at optical fibertermination 108 and collimating lens 109 to achieve the desirableoptical transmission performance. As in the design shown in FIG. 1,conventional fiber ferrule 1 is typically made from a capillary tube.The material compatibility of capillary tube and optical fiber, however,limits the tolerance to harsh environments for these prior art designs.

[0006] In the past, laser sources were a primary limiting factor tooptical fiber system reliability. With the advent of low cost highreliability laser sources for optical fiber systems, some of the passivecomponents in an optical fiber system become primary limiting factors tosystem reliability. It is desirable to improve the reliability andruggedness of passive components, including the optical fibercollimator, to improved system reliability. It is therefore an objectiveof this invention to provide a ruggedized optical fiber collimator.

SUMMARY OF THE INVENTION

[0007] According to this invention, an embodiment of the presentinvention includes a housing, an optical fiber, a collimating lenssystem comprising at least one lens, and an inner tube. The opticalfiber extends into the housing through the inner tube. The housinghouses the inner tube and the collimating lens system. The optical fiberterminates in the housing. The collimating lens system optically couplesto the optical fiber through the optical fiber termination. The housing,the optical fiber, the collimating lens system and the inner tube arearranged to perform the function of an optical fiber collimator. Theinner tube is made from an optical fiber compatible material. Examplesof the optical fiber compatible materials include ruby, quartz, andsapphire.

DESCRIPTION OF THE DRAWINGS

[0008] A better understanding of the invention may be gained from theconsideration of the following detailed description taken in conjunctionwith the accompanying drawings in which:

[0009]FIG. 1 shows the configuration of a conventional optical fibercollimator.

[0010]FIG. 2 shows the configuration of another conventional opticalfiber collimator.

[0011]FIG. 3 shows the configuration of an embodiment of the presentinvention.

[0012]FIG. 4 is a sectional view of a representative housing of theembodiment shown in FIG. 3.

[0013]FIG. 5 shows the configuration of an alternative embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

[0014] In the description that follows, like parts are indicatedthroughout the specification and drawings with the same referencenumerals. The present invention is not limited to the specificembodiments illustrated herein.

[0015]FIG. 3 shows the configuration of an embodiment of the presentinvention and FIG. 4 shows a sectional view of a representative housingof this embodiment. Referring to FIG. 4, housing 101 includes an outertube 121 and inner tube 122. Inner tube 122 has first channel 102. Outertube 121 has second channel 103. First channel 102 and second channel103 are generally rod-shaped and share a common axis. Inner tube 122occupies a portion of second channel 103. Because first channel 102 andsecond channel 103 may have different diameters, there is optionaltransition region 104 between first channel 102 and second channel 103.Entrance to first channel 105 and entrance to second channel 106 aretapered. Housing 101 provides structural support to the embodiment.Inner tube 122 is made from an optical fiber compatible material,including ruby, quartz, and sapphire. The optical fiber compatiblematerial can be precision-laser-drilled and relatively easily polished.Inner tube 122 is permanently bonded to outer tube 121 and it ispermanent part of housing 101.

[0016] Referring to FIGS. 3 and 4, the end portion of optical fiber 107is located in first channel 102 of housing 101. The inner diameter offirst channel 102 is larger than the outer diameter of optical fiber107. Therefore, optical fiber 107 may slide inside first channel 102. Atthe end of optical fiber 107 is optical fiber termination 108. Opticalfiber termination 108 is typically formed by cleaving optical fiber 107.The surface at optical fiber termination 108 is at an angle to the planethat is perpendicular to the optical axis of the end option of opticalfiber 107. The angle may be zero degree. Nevertheless, one skilled inthe art readily understands that by keeping this angle to be positiveand small, typically between one degree and ten degrees, will help toreduce transmission loss and reflection of the embodiment. When the endportion of optical fiber 107 is installed in first channel 102 as shownin FIG. 3, the optical axis of the end portion of optical fiber 107 isthe same as the axis of first channel 102. To further reducetransmission loss and reflection, optical fiber termination 108 has anoptional anti-reflection coating. The conventional fiber ferrule 1 shownin FIGS. 1 and 2 is eliminated in this invention and replaced by innertube 122 that is made from an optical fiber compatible material. Thecross section of collimating lens 109 on the plane that is perpendicularto the optical axis of collimating lens 109 has the shape of a circle.The diameter of this circle is the outer diameter of the body ofcollimating lens 109. At least a portion of collimating lens 109 islocated in second channel 103. The inner diameter of second channel 103is larger than the outer diameter of the body of collimating lens 109.Therefore collimating lens 109 may slide inside second channel 103. Thesurface of collimating lens 109 may have an anti-reflection coating tomaximize optical transmission and minimize reflection.

[0017]FIG. 5 illustrates an alternative embodiment of this invention.Compared to the embodiment shown in FIG. 3, a gradient index (GRIN) lensis used instead of a spherical lens for collimating lens 109 and thehousing employed in this embodiment is a multi-piece housing. Thetwo-piece housing includes first housing and second housing 123. Firsthousing comprises outer tube 121 with inner tube 122 permanentlyattached to it. Second housing holds collimating lens 109. With themulti-piece housing shown FIG. 5, the offset between the optical axis ofcollimating lens 109 and the optical axis of optical fiber 107 atoptical fiber termination 108 can be adjusted during the alignmentprocess. Second housing 123 is usually secured to first housing afterthe alignment process. Compared to the prior art designs, thealternative embodiment does not have a conventional fiber ferrule.

[0018] There are numerous variations to the embodiments above trivial tothe one skilled in the art. Examples of these variations include but arenot limited to:

[0019] the cross section of the channel along the axis of first channel102 is not circular-shaped, common alternatives include polygon-shaped,star shaped, or irregular-shaped;

[0020] the cross section of the channel along the axis of first channel102 is not uniform, common alternatives include tapered or irregular;

[0021] the cross section of the channel along the axis of second channel103 is not circular-shaped, common alternatives include polygon-shaped,star shaped, or irregular-shaped;

[0022] the cross section of the channel along the axis of second channel103 is not uniform, common alternatives include tapered or irregular;

[0023] the entrance to first channel 105 may be tapered or not tapered;

[0024] the entrance to second channel 106 may be tapered or not tapered;

[0025] other types of collimating lenses such as an aspheric lens or anasymmetrical lens are employed as the collimating lens;

[0026] the single collimating lens is replaced by a lens system thatincludes one or more lens elements;

[0027] the lens system has its own supporting structure;

[0028] the cross section of collimating lens 109 on the plane that isperpendicular to the optical axis of collimating lens 109 has a shapeother than that of a circle;

[0029] the collimating lens has shape other than the rod shapeillustrated, such as a Boolean composite comprised of a hemisphere and aright cone connected and aligned at their planer surfaces;

[0030] the alignment of the embodiment includes adjustment other thanthe distance between optical fiber termination 108 and the collimatinglens 109, such as the relative angular orientation about their opticalaxes; and

[0031] optical fiber 107 or collimating lens 109 is attached to housing101 through mechanical methods.

[0032] Further, one skilled in the art readily understands that anyoptical fiber collimator design that employs a conventional fiberferrule, including the ones illustrated in FIGS. 1 and 2, can beruggedized by replacing the conventional fiber ferrule with an innertube that is made from an optical fiber compatible material according tothis invention. The shape of the inner tube may be identical to theshape the conventional fiber ferrule.

[0033] Although the embodiment of the invention has been illustrated andthat the form has been described, it is readily apparent to thoseskilled in the art that various modifications may be made thereinwithout departing from the spirit of the invention.

What is claimed is:
 1. An optical fiber collimator, comprising: ahousing having a first channel and a second channel, said first channelbeing coupled to said second channel; an optical fiber having an opticalfiber termination, a portion of said optical fiber being in said firstchannel and said optical fiber termination being in said housing; and acollimating lens system disposed in said second channel being opticallycoupled to said optical fiber through said optical fiber termination;wherein, said housing, comprising: an outer tube; and an inner tubedisposed at least partially in said outer tube, the channel in saidinner tube being said first channel, and said inner tube is madesubstantially from an optical fiber compatible material selected fromthe group consisting of ruby, quartz, and sapphire.
 2. The optical fibercollimator as claimed in claim 1, wherein, said collimating lens systemcomprises at least one lens.
 3. The optical fiber collimator as claimedin claim 1, wherein, said housing is a multi-piece housing.
 4. Theoptical fiber collimator as claimed in claim 3, wherein, said housingallows for the adjustment of the relative offset between the opticalaxis of said collimating lens and the optical axis of said optical fiberat said optical fiber termination.
 5. An optical fiber collimator,comprising: a housing having an inner tube that is made substantiallyfrom an optical fiber compatible material selected from the groupconsisting of ruby, quartz, and sapphire; an optical fiber extendinginto said housing through said inner tube having an optical fibertermination in said housing; and a collimating lens system disposed atleast partially in said housing being in optical communication with saidoptical fiber through said optical fiber termination.
 6. The opticalfiber collimator as claimed in claim 5, wherein, said collimating lenssystem comprises at least one lens.
 7. The optical fiber collimator asclaimed in claim 5, wherein, said housing is a multi-piece housing. 8.The optical fiber collimator as claimed in claim 7, wherein, saidhousing allows for the adjustment of the relative offset between theoptical axis of said collimating lens and the optical axis of saidoptical fiber at said optical fiber termination.
 9. An optical fibercollimator, comprising: a housing means having an inner tube that ismade substantially from an optical fiber compatible material selectedfrom the group consisting of ruby, quartz, and sapphire; an opticalfiber extending into said housing means through said inner tube havingan optical fiber termination in said housing means; and a collimatingmeans being disposed in said housing means for collimating the lighttraveling from said optical fiber through said optical fiber terminationinto a substantially collimated light beam and collecting light from theoutside of said housing means into said optical fiber.
 10. The opticalfiber collimator as claimed in claim 9, wherein, said housing meanscomprises a housing.
 11. The optical fiber collimator as claimed inclaim 9, wherein, said housing means comprises a multi-piece housinghaving at least two pieces.
 12. The optical fiber collimator as claimedin claim 11, wherein, said housing means comprises: a first housingbeing disposed to house said inner tube; and a second housing beingdispose to house said collimating lens.
 13. The optical fiber collimatoras claimed in claim 9, wherein, said collimating means comprises acollimating lens system.
 14. The optical fiber collimator as claimed inclaim 9, wherein, said collimating lens system comprises at least onelens.